the incastellamento describes less the building of castles than the change towards fortified settlements, in which the castle proper (rocca) is a separate part. The term 'incastellamento' for this process was coined by Pierre Toubert. As in France, it was a different process in the north and the south. In the north, the castles were originally the seats of the barons. They spread quickly after the disruption of royal authority in Italy in the mid-tenth century. By the eleventh century, the territorial magnates, like the margrave of Tuscany, were supreme and castles dotted the landscape. With the rise of the city-states after the collapse of Tuscan power in the early twelfth century, the powerful merchant families began to construct fortress and towers as residences in the cities. Well-preserved San Gimignano was the result of the struggle between Guelphs and Ghibellines. In the centre of the peninsula, the Papal States, the agents of encastellation were not large territorial magnates, but the petty nobles who belonged to various families and factions usually associated with Rome in some way. The Crescentii and the Tusculani constructed fortresses throughout Latium to dominate the roads leading to the Eternal City and the Vatican. During the papal nadir of the tenth and eleventh centuries, their hilltop fortresses gave these minor lords far more power than their territories would otherwise permit. In Rome itself, encastellation often led to the fortifying of the ancient monuments which had fallen into disuses, such as the Arch of Constantine and the Colosseum. These fortresses were usually in the hands of one of the powerful lay families, but sometimes of the popes. In the Mezzogiorno, the independent principalities of the Lombards and the Italian city-states, which distanced themselves from any central authority, formed an opportune place for the proliferation of castles. Indeed, the nominally Byzantine duchies of Gaeta, Naples, and Amalfi grew around what were originally small coastal fortresses. The decline of ducal authority in these places has been blamed on the tendency to give outlying regions to younger sons (e.g. Docibilis II of Gaeta granting Fondi to Marinus), who then built their own fortresses and thus became independent in fact. Historian G. A. Loud considers incastellamento as one of the chief reasons for the decline in princely influence in Benevento and Capua (especially the former) during the late tenth century. Historian Barbara Kreutz notes the encastellation of the monastic estates which dominated